The “Latest posts” feature only appears for certain websites (TechCrunch, New York Times, etc), and appears to be different than the “Top Headlines” feature that shows not the latest headlines, but perhaps the most popular ones?
In the screenshot above you can see that a search on “New York Times” shows both lists, with the “latest posts” showing results from minutes or hours ago, and “Top headlines” showing results filtered by something other than time.
We don’t have “Latest posts” showing up on a search for “LiveSide” (hey!, what’s up with that?) and it seems to be kind of hit or miss as to who has the new feature at this point, but it seems like it could be quite useful. We’ll keep an eye on it.